<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .d1{
        width: 300px;
        height: 100px;
        padding: 50px;
        border: 1px solid black;
        border-radius: 5px;
    }
    .d2{
        width: 300px;
        height: 100px;
        border: 1px solid black;
        border-radius: 5px;
    }
    .d3{
        width: 300px;
        height: 100px;
        padding: 50px;
        border: 1px solid black;
        border-radius: 5px;
        /*  */
        box-sizing: border-box;
    }
</style>
<body>
    <div class="d1">d1</div><br>
    <div class="d2">d2</div><br>
    <div class="d3">d3</div>
</body>
</html>